Materials with a porous structure have been extensively used as a carrier for catalysts and a carrier for fixedly supporting enzymes or functional organic compounds thereon because of a large surface area thereof. In particular, the materials with a porous structure having a sharp pore size distribution exhibit a function as a molecular sieve and are therefore usable in the applications such as a carrier for catalysts having a structural selectivity or a separating agent for various materials. In such applications, there is a demand for porous materials having uniform and fine pores.
As the porous materials having uniform and fine pores, mesoporous silica having meso-order pores has been developed. It has been noticed that the mesoporous silica is used in the applications such as nanowires, semiconductors and optical electronics in addition to those described previously.
Patent Document 1 discloses (i) a mesostructure having tubular mesopores which are oriented in the direction parallel with a surface of a polymer substrate and (ii) a method for forming a mesostructure having mesopores oriented in a given in-plane direction on a surface of a polymer substrate which includes the step of hydrolyzing an alkoxide under the condition that the oriented polymer surface is kept in contact with a surfactant and a liquid containing the alkoxide.
However, in the mesostructure, the mesopores are oriented in parallel with the surface of the substrate. Therefore, the mesostructure is usable as a highly-functional structure only in the limited applications.
On the other hand, Non-Patent Document 1 discloses a mesostructure which is produced by vertically orienting a micelle on a glass substrate in a ferromagnetic field. In view of a lattice spacing of the mesostructure as measured by a powder X-ray diffraction (XRD) method, it is suggested that the size of mesopores in the obtained mesostructure is as large as 5 nm or more.
Thus, there have been conventionally obtained no mesoporous silica films in which mesopores having an average pore period of 5 nm or less are oriented perpendicular to a substrate.
Patent Document 1: JP 2001-58812A
Non-Patent Document 1: “Journal of Materials Chemistry”, 2005, 15, 1137-1140